Yarn by extruding polyamide fibers and sulfonated polyester concentrate

ABSTRACT

A fiber-forming polyamide composition contains a fiber forming polyamide and a sulfonated polyester concentrate, the concentrate disabling and dye sites in the polyamide so that fibers formed from the composition will have enhanced stain and soil resistance. The sulfonated polyester concentrate contains a reagent, preferably an alkali metal salt of 5-sulfoisophthalic acid, and thermoplastic polyester, preferably one or more of PET, PTT, PBT, PETG and poly(ethylene terephthalate-co-isophthalate).

CROSS-REFERENCED TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 09/593,665,filed Jun. 14, 2000, U.S. Pat. No. 6,334,877, which was a divisional ofapplication Ser. No. 09/190,143, filed Nov. 12, 1998, U.S. Pat. No.6,133,382, which was a continuation-in-part of application Ser. No.08/522,123, filed Aug. 31, 1995, allowed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to stain resistant and soil resistant polyamidecompositions and fibers formed therefrom, the fibers being particularlyuseful in the manufacture of textile articles, carpets andfloorcoverings.

2. The Prior Art

Carpet yarns prepared from polyamide fibers are subject to staining by avariety of foods, drinks and many other compositions with which it comesin accidental contact. The uptake of acid dye stains from, for example,soft drinks, is a particularly vexing problem for polyamide fibers dueto the availability therein of acid dye sites such as amine end groupsand amide linkages. Several methods have been suggested for enhancingthe resistance of polyamide fibers to acid dye stains. One approach isto apply a so-called topical “stain blocker” coating to the surfaces ofthe polyamide fibers to prevent access to the acid dye sites therein bythe acid dye staining composition. One of the main types of topicalstainblocker are sulfonated aromatic condensates (SAC). There are anumber of patents covering SACs. Examples of the method include U.S.Pat. Nos. 5,145,486, 4,680,212 and 4,780,099. Polyamides that aretopically coated with SACs have the disadvantage that the topicalcoating is removed during use and maintenance. Gradual removal of thecoating will also occur during cleaning with water and detergents.Fibers used for carpet applications may be regularly cleaned withalkaline-based cleaning agents. SAC topical coatings are easily removedusing these types of cleaning agents. The topical coating will also begradually removed during normal wear of the fiber. In addition to theirremoval during use and maintenance, SACs generally have inferiorresistance to light, oxides of nitrogen, and bleach, the latter beingcommonly used for the cleaning of industrial textiles and carpets. Also,the base color of SACs is not colorless and thus may change the shade ofthe color of the yarn.

Another approach for enhancing the resistance of polyamide fibers toacid dye stains is to form the fibers from polyamides prepared bycopolymerizing monomers, some of which contain sulfonate moieties.Typical of such systems are those disclosed in U.S. Pat. Nos. 3,542,743,3,846,507, 3,898,200, 4,391,968, 5,108,684, and 5,164,261 and EP517,203. All of these prior art patents teach that aryl sulfonate units,when added at the start of the polymerization with the other desiredmonomers, act as comonomers and become integral parts of the polyamidechain. All of these patents are concerned with modifying the dyeing orstain resistant characteristics of the polyamide.

Fibers are generally prepared from polyamides by melt spinning.Sulfonate-containing polyamides generally have higher melt viscositiesthan non-sulfonate-containing polyamides for equivalent relativesolution viscosities, which limits the extent of polymerization that canpractically be achieved in batch autoclave reaction vessels due to theretardation thereby of the rate of polymerization, as well as hinderanceof effective discharge of the polymerized melt from the reactor. Inaddition, the presence of sulfonates which have surfactant propertiespromotes excessive foaming during the melt polymerization process,resulting in poor agitation of the reaction mixture and non-uniformityof product. An additional disadvantage associated withsulfonate-containing polyamide copolymers is that they are generallymore difficult to dry than sulfonate-free polyamides due to thehygroscopic nature of the sulfonate groups.

Yarns having different depths of color require different levels of stainprotection. Thus, light shaded colors show the presence of stains morethan darker colors. It would be advantageous, therefore, to be able toprovide different levels of stain resistance to polyamides dependingupon the ultimate yarn color without having to provide a separatepolyamide feedstock for optimum formulation of each color yarn.

In addition to the problems of staining of polyamide fibers, soiling ofpolyamide fibers is also an issue. Fibers used in textile, carpet andflooring applications are desirably low in soil pick-up, i.e., the fiberdoes not attract soil, and secondly the fiber is easy to clean once itis soiled. Soil proofing of polyamides typically involves one of twoapproaches. Firstly, a coating may be placed on the fiber which is“sacrificial” in nature, i.e., it is designed to pick up soil, but thenmust be removed in a cleaning process. Starch is a well known and longpracticed example. Such an approach has the drawback that the fiberneeds to be recoated after each cleaning to maintain its soilresistance. The second approach to soil proofing is the use of adifferent type of coating to change the surface energy orhydrophilic/hydrophobic balance of the polyamide, thus making it lessattractive to soil. Fluorinated compounds are the most favored speciesin this area, applied as a topical coating to the fiber. Thefluorochemical compounds are coated onto the fiber to prevent or reducethe wetting of the surface by minimizing the contact between the fibersurface and substances that can soil the fiber, making the substanceeasier to remove. Examples of patents in this area include U.S. Pat.Nos. 3,816,167, 3,896,035, RE30,337 and 4,043,964. The use of topicalcoatings of the latter type have the similar disadvantages to SACs inthat they are removed from the carpet during use, routine maintenanceand cleaning.

It is an object of the present invention to provide a novel and highlyadvantageous approach for imparting stain resistance to fibers formedfrom polyamides. It is yet another object of the present invention toprovide stain resistant polyamide fibers with improved soil resistancein that they have low affinity for soil attraction, and if soiled, arethen easy to clean.

SUMMARY OF THE INVENTION

According to the present invention acid dye stain-resistant andsoil-resistant polyamide fibers are formed from a polyamide compositioncomprising a fiber-forming polyamide and a sulfonated polyesterconcentrate consisting essentially of a reagent melt compounded with athermoplastic polyester, the polyamide fibers being advantageouslyformed by melt spinning, drawing and texturing. The invention includesthe polyamide composition used in the method and the articles ofmanufacture produced from the fibers of the invention, particularlytextile articles, carpets and floorcoverings.

DETAILED DESCRIPTION OF THE INVENTION

The terms below have the following meanings herein, unless otherwisenoted:

“Reagent” refers to a chemical compound, composition or material whichassociates (as that term is defined below) with the free acid dye sitesin a fiber-forming polyamide to thereby render them unavailable forassociation with an acid dye, which reagent is incapable itself ofassociating with or taking up the acid dye.

“Association” refers to the chemical reaction or bonding between thereagent and the free acid dye sites in the polyamide which results inprevention of “taking up” of the acid due by the polyamide, i.e.,staining. The association may take the form of a chemical reaction or anacid-salt formulation. Additional types of association include hydrogenbonding, dipole—dipole interaction, Van der Waals forces andcoordination complexing.

“Acid dye stain” refers to any material or composition which functionsas an acid dyestuff by reacting or associating with the free dye sitesin polyamides to substantially permanently color or stain the latter.

The term “acid dye sites” refers to those basic sites in polyamides,e.g., amine end groups, amide linkages, etc., which react or associatewith acid dyes, thereby resulting in staining of the polyamide.

“Disabling” the acid dye sites from taking up acid dye stains refers tothe effect of the association between the reagent and the acid dye siteswhich renders the latter less capable of associating with acid dyes suchas, for example, those in soft drinks, tomato-based products, etc.,which result in staining.

The present invention is predicated on the discovery that optimum levelsof resistance to acid dye stain and improved soiling resistance may beimparted to polyamide fibers by melt compounding a sulfonated polyesterconcentrate with fiber-forming polyamide compositions subsequent topolymerization of the polyamide and prior to the formation of thefibers. The invention thereby enables avoidance of the above enumerateddisadvantages associated with coating the polyamide with stain resistantSACs, formation of the polyamides by copolymerizing sulfonate containingmonomers and with topical application of soil resistant fluorochemicalformulations.

The compositions are prepared by initially melt compounding a reagent(discussed below) with a polyester thermoplastic resin using an extruderunder certain conditions defined hereinafter to produce a sulfonatedpolyester concentrate. The sulfonated polyester concentrate is then meltcompounded with a fiber-forming polyamide in a fiber spinning extruderto produce a sulfonated polyamide. Product fibers made according to theinvention show durable stain-resistant properties equivalent to thoseproduced according to the prior art methods without the consequentdisadvantages attendant thereto. The product fibers have soil resistancesuperior to the prior art methods.

The thermoplastic polyester may be any thermally stable melt processablepolyester that has a melting point temperature preferably less than 270°C. Preferred polyesters for preparation of the concentrate arepoly(ethylene terephthalate) known as PET, poly(trimethyleneterephthalate) known as PTT, poly(butylene terephthalate) known as PBT,poly(ethylene terephthalate-co-isophthalate) and copolyesters ofpoly(ethylene terephthalate) and 1,4-cyclohexanedimethanol known asPETG.

The reagent is a metal salt of sulfoisophthalic acid, preferably analkali metal salt and most preferably the sodium and lithium salts of5-sulfoisophthalic acid. Other metal salts of sulfoisophthalic acid canbe used, including alkaline earth and transition metal salts ofsulfoisophthalic acid.

The invention is applicable to any fiber-forming polyamide. Thepreferred polyamides are PA6 and PA66, copolymers of PA6 and PA66, ormixtures thereof.

During development of the present invention it was found that, if thereagent is melt compounded directly into either a PA6 or PA66 resin toform a sulfonated polyamide concentrate, then substantial degradation ofthe polyamide took place as determined through solution relativeviscosity measurement. In addition, the % reagent that could becompounded into the PA6 or PA66 was limited to about 20% by weight ofthe total weight of the sulfonated polyamide concentrate. The productfiber formed by drawing and texturing fiber-forming polyamide when thesulfonated polyamide concentrate was added thereto on the fiber meltspinning line displayed poor stain resistance and only average soilingperformance.

Other types of polyamides that have a lower propensity to hydrolyticdegradation can be successfully used to form a sulfonated polyamideconcentrate such as PA11 and PA12 but do not show unexpectedly improvedsoiling performance.

In addition, during development of the present invention, up to 10% ofvarious thermoplastic polyesters were added to sulfonated polyamideswhere the sulfonate units when added at the start of the polymerizationwith the other desired monomers, and also to unsulfonated PA66 resins,i.e., resins that are polymerized essentially from adipic acid andhexamethylene diamine or the nylon salt of adipic acid and hexamethylenediamine. No unexpectedly improved soiling performance resulted.

The reagent may be combined with the polyester in any suitable form suchas powdered, pelletized, encapsulated, etc. The polyester may beemployed as a powder, granules or pellets. The reagent and the polyesterare preferably combined employing a melt extruder and, most preferably,a screw-type extruder. Optimally, a twin-screw extruder of the fullyintermeshing type with both screws rotating in the same direction(co-rotating) is employed, although other types of twin-screw extrudersmay be used such as counter-rotating and/or non-intermeshing types.Single screw extruders may also be employed. The extruder preferably hasa barrel length to diameter ratio of at least 24:1; however, it will beunderstood that any suitable ratio may be employed depending upon theparameters of the particular compounding process contemplated.

While it is no way intended to limit the invention by the soundness oraccuracy of any theory set forth to explain the nature of the invention,it is postulated that, during the processing step(s), the sulfonatedpolyester concentrate at least partially associates with, or reactswith, reactive chemical groups or acid dye sites on the polyamide, suchas amine end groups or amide linkages. Removal of volatiles from thecompounding mixture of reagent and polyester aids the subsequentassociation and/or reaction with the polyamide. This removal ofvolatiles is achieved preferably by the presence of one or more vents onthe extruder barrel. The optimum position of the vent ports on thebarrel is determined by the extruder screw profile and the barrel lengthto diameter ratio used. The extraction of volatiles through the ventport is preferably vacuum assisted with a vacuum level of greater than10 in. Hg and preferably greater than 20 in. Hg. The rate ofdevolatilization can be assisted through substantially dry nitrogen orinert gas injection through an inlet port on the barrel either upstreamor downstream of the vent port. Under this situation, a lower vacuumlevel may be acceptable. Additional ways of promoting the subsequentassociation and/or reaction with the polyamide are through controlleddrying of the feedstocks, addition of water scavenging additives, or acombination of the methods discussed hereinabove. The reagent and thepolyester are preferably dried prior to melt compounding to a moisturecontent of less than 1000 ppm. The sulfonated concentrate prepared maycontain from 10% up to about 65% by weight of reagent by total weight ofthe concentrate, though it is preferably in the range of 20% to 50%weight of the reagent by total weight of the concentrate.

The sulfonated polyester concentrate is then dried prior to fiber meltspinning. The preferred moisture content of the concentrate prior tomelt spinning is less than 500 ppm, and most preferably less than 100ppm. The sulfonated polyester concentrate is easy to dry in comparisonto sulfonated polyamides in that higher drying temperatures can be usedto dry the polyesters than polyamides without degradation occurring thatmay be detrimental to the fiber-forming process and the properties ofthe product fibers. The concentrate is then melt compounded with apre-dried fiber-forming polyamide. The amount and ratios offiber-forming polyamide to concentrate may be varied according todesired needs. Generally, it is preferred to employ combinationscontaining about 1000 up to a maximum of about 3,000 ppm sulfur. Thepolyamide should have a relative solution viscosity (RV) of greater than2.9 and preferably greater than 3.1 and less than 4.0. The RV of thepolyamide is determined by first preparing a 0.55% weight by weightsolution of the pre-dried polyamide in 96% sulfuric acid. Solution flowtimes are determined in a Cannon-Ubbelohde size 2 viscometer suspendedin a temperature controlled water bath set at a temperature of 25°C.±0.02° C. The flow times of the sulfuric acid are also measured. TheRV is calculated by dividing the flow time of the polyamide solution bythe flow time of the sulfuric acid. The polyamide is typically producedby melt polymerization, although other methods known to those ordinarilyskilled in the art such as, e.g., solution polymerization, may be used.The desired RV may be achieved wholly through melt polymerization or atwo-step process may be employed, i.e., melt polymerization to an RVvalue lower than that desired, followed by solid state polymerization tothe desired value. The polyamide should also have an amine end group(AEG) level of less than 35 equivalents per 10⁶ g and preferably lessthan 30 equivalents per 10⁶ g. The AEG level is determined by means of apotentiometric titration. A known weight of sample is dissolved inm-cresol and titrated against 0.1 M perchloric acid in methanol. A blanktitration is also carried out on the m-cresol and used to correct thesample titer. The polyamide is preferably dried to a moisture content ofless than 1000 ppm. The concentrate is mixed with the polyamide in thedesired ratio depending on the level of stain resistance required in thefiber product.

Alternatively, the polyamide and the sulfonated concentrate may becombined in a prefiber spinning compounding operation or directly in thefiber melt spinning stage. The fiber melt spinning process of aconventional type is used, familiar to those skilled in the art.Functional additives may be added during the fiber formation processsuch as colorants, anti-oxidants, stabilizers, antimicrobials, meltviscosity enhancers, nucleating agents, antistatic agents, processingaids, flame retardants or mixtures thereof. The spun fiber may then betextured using air-jet texturing or mechanical crimp texturing. Productfibers made according to the invention show durable stain resistantproperties equivalent to those produced according to prior art methods.The product fibers have soil resistance that is superior to thoseproduced according to prior art methods.

Only a small proportion of the reagent is reacted with the fiber-formingpolyamide. The bulk of the reagent is dispersed/associated with theresin. It is desired that a proportion of the reagent is reacted withthe fiber-forming polyamide. Polyamide copolymers are conventionallyproduced by a condensation polymerization where water (or other smallvolatile molecule, depending on the chemistry) is generated as aby-product. In order to drive this equilibrium reaction forward, it isnecessary to remove this water by-product from the system below theequilibrium water concentration. If this achieved in the fiber meltspinning line, then association/reaction of the reagent in theconcentrate with the fiber-forming polyamide will occur. In fiber meltspinning lines, either vented or non-vented extruder barrels can beused. The water concentration can be reduced to below the equilibriumvalue by any of the methods discussed hereinabove. The fiber meltspinning, drawing and texturing processes used are conventional in typeand familiar to those ordinarily skilled in the art.

Extraction analysis on the fibers of the invention have shown that thereagent is permanently fixed in the polyamide matrix as discussed in theExamples given below.

Either the fibers or yarns prepared from this invention may bemanufactured into novel textiles, carpets and other articles ofmanufacture requiring polyamides with enhanced resistance to staining byacid dyestuffs or enhanced soiling resistance according to conventional,well known methods. The textured yarn is most ideally used to produce acarpet using methods of manufacture known to those ordinarily skilled inthe art, including tufting, weaving, bonding, needle-loom and knitting.Detailed descriptions of these methods can be found at pages 134 to 140of “Synthetic Fiber Materials,” edited by H. Brody, published byLongman, 1994, the disclosure of which is incorporated by reference.

In the following examples, a standard test is used to evaluate the stainresistance of the yarn formed. It involves the use of an acidifiedsolution of FD & C Red 40 dye which is present in the soft drink cherryflavored Kool-Aid® commercially sold by Kraft General Foods, Inc.

Red 40 Stain Test

0.1000 g±0.0030 g of FD & C Red 40 dye (CI Food Red 17) is dissolved in1,000 cm³ of distilled water. The pH of the dye solution is adjusted tobetween 2.80 and 2.90 by making small additions of technical gradecitric acid. The pH adjusted solution is allowed to reach ambienttemperature, i.e., 21° C.±1° C., prior to use. The carpet is laid on ahard, flat non-porous surface. 50 mls±1 ml of the Red 40 dye solution ispoured into a 2 inch ring placed on the carpet. A plunger is insertedinto the ring and is moved up and down 5 times without rotation toensure that the application of the solution is even and the fibers arefully wetted. The ring is removed and the carpet is left to air dry for24 hours at ambient temperature. The carpet is then washed with runningmains water of a temperature of 45° C.±5° C. for 2 minutes. As much aspossible of the water is removed using a vacuum extractor. The carpet isthen left for a further 24 hours to air dry at ambient temperature. Ifred dye wicks to the surface of the carpet during this drying periodthen the washing steps indicated above are repeated. The stainresistance of the carpet face yarn is determined by visual comparison tothe AATCC Red 40 Stain Scale, which is available from the AmericanAssociation of Textile Chemists and Colorists (AATCC), Research TrianglePark, N.C. The scale consists of ten transparent film squares coloredwith gradually increasing strengths of FD & C Red 40 numbered from 1 to10 with 1 being the strongest color and 10 being colorless. A sample ofthe unstained carpet is placed underneath the colored portions of thescale and the stained carpet is placed underneath the colorless portionof the scale and viewed under the daylight or equivalent illuminant. Thelight should be incident upon the surfaces at an angle of 45°±5° and theviewing direction should be 90°±5° to the plane of the surfaces. Thestained carpet is compared to the unstained carpet placed under theclosest numbered colored square of the stain scale so that the bestcolor match is obtained. If the color of the stained carpet fallsbetween two squares on the scale, then half grades are given. The numberof this colored square, or squares of the match falls between twosquares, is called the Stain Rating.

Carpet Wear Testing

Tufted carpet was tested per ASTM Test Method D5252-92 to 50,000revolutions at 70° F. and 50% R.H. An Electrolux upright vacuum cleanermodel LXE was used to vacuum the carpet after the test and beforegrading. The carpet was not vacuumed after every 2000 revolutions asdetailed in the ASTM Test Method. The worn carpet samples were gradedusing the Carpet and Rug Institute Reference Scale A. This scaleconsists of four photographs numbered from 1 to 4 showing graduallyincreasing degrees of wear, appearance deterioration or matting. A gradeof 1 indicates a badly worn sample. A grade of 5 indicates that no wearhas occurred. If the tested sample falls between two photographs, then ahalf grade is given. For example, if the degree of wear falls betweenphotographs 3 and 4 then a grade of 3.5 is given. This test is known bythose of ordinary skill in the art to simulate human foot traffics. Onerevolution of the test drum is considered to be equivalent to 8-12 foottraffics.

Soiling Test

Tufted carpet was tested for soiling using the similar apparatus to thatused for the carpet wear testing method given above. 1.5000±0.0020 g ofSPS-2001 Standard Carpet Dry Soil available from 3M, St. Paul, Minn.,was sprinkled evenly over carpet of dimensions 25.5 inches by 8.25inches using a fine sifter. The carpet was carefully placed inside thetest drum and 150 of 5.03±0.03 g of clean, soil-free flint pellets wereadded to the drum. The lid of the drum is secured and the drum is placedon the drum roller. The drum is rolled for 500 rotations which is called1 soiling cycle. The carpet was then removed from the drum and vacuumedwith the handheld Beaterbar of an Electrolux upright vacuum cleanermodel LXE. The soiled and vacuumed carpet was graded using the AATCCGrey Scale for Staining. The scale consists of 10 pairs of greyrectangles, the pairs representing progressive differences in color orcontrast. The scale runs from 1 to 5 in half unit grades, with a valueof 1 indicating gross change in color or contrast, and 5 being no coloror contrast change. The test may then be repeated as desired to evaluatethe effect of multiple soiling cycles. The soiled carpets are thenevaluated for ease of cleaning with hot mains water (55° C.±5° C.) usingthe Deluxe Hand Tool of a Windsor® Passport™ wet extractor (carpetcleaner) supplied by Windsor Industries, Inc., Englewood, Colo. Nodetergent or other cleaning agent other than water is used in theevaluation. Five passes of the Hand Tool using the water spray and wetextraction are done in opposite directions over the carpet. The carpetis then left for 24 hours to air dry at ambient temperature beforegrading using the AATCC Grey Scale for Staining.

Colorfastness to Oxides of Nitrogen Test

Colorfastness to oxides of nitrogen was tested using AATCC Test Method164-1997, for 1, 3 and 5 cycles, at a temperature of 40° C.±1° C., and arelative humidity of 87.5±2.5%.

Accelerated Ultraviolet (UV) Light Weathering

Colorfastness to UV light was tested using AATCC Test Method 16, OptionE. The face yarn side (front) of the carpet sample is exposed. The backof carpet sample is covered (backed) to prevent exposure. The acceptanceof the result is not compared to a reference sample. The specimen iscompared to the masked portion of the specimen. The colorfastness tolight rating is determined using the AATCC Gray Scale for Color Change.The ambient (dry bulb) temperature is 43° C.±2° C., the black paneltemperature is 63° C.±1° C. and the relative humidity is 30%±5%. Theexposure is controlled by the AATCC Blue Wool Lightfastness Standard L4.The radiant energy is 1.10±0.03 W/m² at 420 nm. The total radiant energyis 170 kJ with an elapsed exposure time of 85 hours. The type of testapparatus is a xenon-arc, manufactured by Atlas Electric Devices Co.,Model No. 65-WR, Serial No. XE-523FC, with a 2-tier specimen rack and adistilled water supply.

Bleach Test

The carpet is laid on a hard, flat non-porous surface. 20 mls±1 ml ofClorox® (a registered tradename of The Clorox Company, Oakland, Calif.)regular bleach, containing 5.25% of sodium hypochlorite and 94.75% ofinert ingredients, is poured into a 2 inch ring placed on the carpet. Aplunger is inserted into the ring and is moved up and down 5 timeswithout rotation to ensure that the Clorox application is even and thefibers are fully wetted. The ring is removed and the carpet is left toair dry for 24 hours at ambient temperature. The carpet is then washedwith running water of a temperature of 45° C.±5° C. for 2 minutes. Asmuch as possible of the water is removed using a vacuum extractor. Thecarpet is then left for a further 24 hours to air dry at ambienttemperature. The carpet is then graded using the AATCC Gray Scale forColor Change.

Reagent Extraction Test

5.0000 g±0.0010 g of yarn is placed in 100 mls of methanol in apre-weighed round bottomed flask and fitted with a condenser. Themethanol is heated to boiling reflux for 16 hours. The yarn is removedfrom the methanol and washed with 2×50 mls aliquots of methanol whichare added to flask containing the refluxed methanol. The methanol in theflask is evaporated to dryness. The weight of any residue is thendetermined.

The invention is illustrated by the following non-limiting examples.

EXAMPLES

The following yarn spinning, draw-texturing and carpet tufting methodswere applied to the examples.

Yarn Spinning

Undrawn yarns were spun using an unvented melt spinning extrusion systemof a type and configuration known to those skilled in the art. Thepolymer melt was filtered through a screen pack containing a 50×250 meshscreen prior to being metered to a 60 hole die with trilobal (Y) shapedholes. The 60 filaments produced were separated into 2×30 filamentbundles, spin finish applied, and the two bundles wound up onto separatewinders to produce an undrawn yarn with a denier of 1850 g/9000 m with afilament count of 30, (“1850/30Y”).

Yarn Draw-Texturing

4 ends of the 1850/30Y undrawn yarn produced were cotextured usingmechanical crimp draw-texturing at a draw ratio of 3.6 to give a2400/120Y bulked continuous filament (BCF) yarn.

Carpet Tufting

The BCF yarn was tufted into a {fraction (1/10)}^(th) gauge, {fraction(3/16)} inch pile height level loop carpet construction and back with alatex backing, to give an approximate yarn face weight of 20 oz. In thecourse of the development work carried out in pursuance of the presentinvention it has been found that different types of backing may resultin different properties of the face yarn of the carpet, including wearand stain resistance performance. In the Examples given below, the samelatex backing has been used for all carpets produced. The latex is STIX320™ Custom Rug Laminating Adhesive supplied by XL Corp., Calhoun, Ga.

Examples 1 to 4 (Comparative Example)

A sulfonated PA66 resin, polymerized from the nylon salt of adipic acidand hexamethylene diamine, with 5-sodiosulfoisophthalic acid, containing2,300 ppm of sulfur, with an RV=2.7, and a moisture level of 650 ppm,was melt spun, drawn and textured. A formulated masterbatches containingvarious pigments were added during the melt spinning stage to give theyarn a beige coloration (“Light Wheat”). A copper/iodide basedstabilizer was also added. 0.3% oil on yarn of Lurol NF-6239 spin finishsupplied by Goulston Technologies, Monroe, N.C., was applied to the yarnwith various levels of Scotchguard FC-248 supplied by 3M, St. Paul,Minn. The level of spin finish was determined by an FTIR method. Theamount of fluorine on the yarn was determined by a combustion method.The yarns were tufted in carpet and tested for Red 40 staining, soiling,wear, colorfastness to oxides of nitrogen and accelerated UV weathering.The results are given in Table 1.

Example 5 (Comparative Example Showing that Use of Polyamide in theSulfonated Concentrate Does Not Provide Surprising or Unexpected ResultsOver Prior Art)

A PA66 resin, polymerized from the nylon salt of adipic acid andhexamethylene diamine, with an RV=3.2 an AEG level of 27 equivalents per10⁶ g and a moisture level of less than 500 ppm was melt compounded with10% wt. of the lithium salt of 5-sulfoisophthalic acid (LiSIPA) alsodried to a moisture level of 170 ppm. The melt compounding was carriedout in a 40 mm co-rotating twin-screw extruder with a length-to-diameterratio of 24:1 which was vented with vacuum assistance of 22 in. Hg. Thesulfonated polyamide concentrate produce strand produced from theextrusion process was extremely brittle and difficult to pelletize. TheRV of the sulfonated polyamide concentrate was 2.0. 20% of thissulfonated polyamide concentrate was added to the same polyamide resinfeedstock used to make the concentrate and melt spun, drawn andtextured. 0.3% oil on yarn of Lurol NF-6239 spin finish containing 0.13%of Scotchguard FC-248 was applied to the yarn. The yarn produced wastufted into carpet and tested for Red 40 staining. The stain rating ofthe face yarn on the carpet was 4.0.

Example 6 (Comparative Example Showing the Poor Stain Resistance ofUnsulfonated Polyamide)

The same PA66 used in Examples 1 to 4 was melt spun, drawn and texturedwithout the addition of sulfonates. 0.3% oil on yarn of Lurol NF-6239spin finish containing 0.13% ppm of Scotchguard FC-248 was applied tothe yarn. The yarn produced was tufted into carpet and tested for Red 40staining. The stain rating of the face yarn on the carpet was 4.0.

Example 7 (Comparative Example Showing that the Addition of PBT toSulfonated Polyamide Does Not Provide Surprising or Unexpected Results)

10% of PET with an IV=0.67 and pre-dried to a moisture level of lessthan 50 ppm was added to the sulfonated PA66 resin of Examples 1 to 4and melt spun, drawn and textured. 0.3% oil on yarn of Lurol NF-6239spin finish containing 0.13% of Scotchguard FC-248 was applied to theyarn. A formulated off-white pigment concentrate (“Ceiling White”)containing copper/iodide stabilizer was also added during the spinningprocess. The yarns were tufted into carpet and tested for Red 40staining, soiling, wear, colorfastness to oxides of nitrogen andaccelerated UV weathering. The results are given in Table 2.

Example 8 (Comparative Example Showing that the Addition of PBT toSulfonated Polyamide Does Not Provide Surprising or Unexpected Results)

10% of PBT and pre-dried to a moisture level of 80 ppm was added to thepre-dried sulfonated PA66 resin of Examples 1 to 4 and melt spun, drawnand textured. 0.3% oil on yarn of Lurol NF-6239 spin finish containing0.13% of Scotchguard FC-248 was applied to the yarn. The same CeilingWhite pigment concentrate containing copper/iodide stabilizer of Example7 was also added during the spinning process. The yarns were tufted incarpet and tested for Red 40 staining, soiling, wear, colorfastness tooxides of nitrogen and accelerated UV weathering. The results are givenin Table 2.

Example 9 (Comparative Example Showing that the Addition of PET toUnsulfonated Polyamide Does Not Provide Surprising or UnexpectedResults)

10% of PET of Example 7 was added to the pre-dried (unsulfonated) PA66resin of Example 5 and melt spun, drawn and textured. 0.3% oil on yarnof Lurol NF-6239 spin finish containing 0.13% of Scotchguard FC-248 wasapplied to the yarn. The same Ceiling White pigment concentratecontaining copper/iodide stabilizer of Example 7 was also added duringthe spinning process. The yarn produced was tufted into carpet andtested for Red 40 staining. The stain rating of the face yarn on thecarpet was 4.5.

Example 10 (Comparative Example Showing that the Addition of PBT toUnsulfonated Polyamide Does Not Provide Surprising or UnexpectedResults)

10% of PBT of Example 8 was added to the pre-dried (unsulfonated) PA66resin of Example 5 and melt spun, drawn and textured. 0.3% oil on yarnof Lurol NF-6239 spin finish containing 0.13% of Scotchguard FC-248 wasapplied to the yarn. The same Ceiling White pigment concentratecontaining copper/iodide stabilizer of Example 7 was also added duringthe spinning process. The yarn produced was tufted into carpet andtested for Red 40 staining. The stain rating of the face yarn on thecarpet was 4.5.

Examples 11 to 14

Four different sulfonated polyester concentrates were prepared from PET,PBT, PTT and PETG. The PETG had a softening point of 78° C. Each of thefour concentrates were prepared and evaluated in a fiber-formingpolyamide resin in the following manner. The polyester and5-sodiosulfoisophthalic acid (50:50 weight basis) of a moisture level ofless than 1000 ppm were melt compounded in a 30 mm twin-screw extruderwith a length to diameter ratio of about 30:1 which was vented withvacuum assistance of between 15 to 20 in.Hg. Continuous strand wasproduced from the extruder that was easy to pelletize. The sulfonatedpolyester concentrate produced was dried to a moisture level of lessthan 100 ppm, except for the concentrate containing PETG which was driedto a moisture level of 450 ppm. The concentrate was added at a level of4% by weight to the (unsulfonated) PA66 resin of Example 5 during themelt spinning process. The same Ceiling White pigment concentratecontaining copper/iodide stabilizer of Example 7 was also added duringthe spinning process. The undrawn yarn produced was draw-textured. 0.3%oil on yarn of Lurol NF-6239 spin finish containing 0.13% of ScotchguardFC-248 was applied to the yarn. The yarns were tufted in carpet andtested for Red 40 staining, soiling, wear, colorfastness to oxides ofnitrogen and accelerated UV weathering. Example 11 yarn was preparedusing a sulfonated polyester concentrate from PETG. Example 12 yarn wasprepared using a sulfonated polyester concentrate from PBT. Example 13yarn was prepared using a sulfonated polyester concentrate from PTT.Example 14 yarn was prepared using a sulfonated polyester concentratefrom PET. The results are given in Table 2. The yarns produced fromExamples 11 to 14 were subjected to the Reagent Extraction Testdescribed above. No residue was recorded for these four Examples.

Example 15 (Further Comparative Example)

The sulfonated PA66 resin of Example 1 was melt spun with the sameCeiling White pigment concentrate containing copper/iodide stabilizer asExamples 10 to 13 and the undrawn yarn then draw-textured. 0.3% oil onyarn of Lurol NF-6239 spin finish containing 0.13% of Scotchguard FC-248was applied to the yarn. The same Ceiling White pigment concentratecontaining copper/iodide stabilizer of Example 7 was also added duringthe spinning process. The yarns were tufted in carpet and tested for Red40 staining, soiling, wear, colorfastness to oxides of nitrogen andaccelerated UV weathering. The results are given in Table 2. The yarnwas subjected to the Reagent Extraction Test described above. No residuewas recorded for this Example.

Example 16 (Further Comparative Example)

The unsulfonated PA66 resin of Example 4 was melt spun with the sameCeiling White pigment concentrate containing copper/iodide stabilizer ofExample 7 and the undrawn yarn then draw-textured. 0.3% oil on yarn ofLurol NF-6239 spin finish containing 0.13% of Scotchguard FC-248 wasapplied to the yarn. The yarns were tufted in carpet and tested for Red40 staining, soiling, wear, colorfastness to oxides of nitrogen andaccelerated UV weathering. The results are given in Table 2. The yarnwas subjected to the Reagent Extraction Test described above. No residuewas recorded for this Example.

TABLE 1 Wear Bleach Soil Resistance Ratings Red 40 Appear- Color UVLight 1 cycle 1 cycle 3 cycles 3 cycles 5 cycles 5 cycles ExampleFluorine Stain ance Change Weather- dry wet ex- dry wet ex- dry wet ex-Colorfastness to NOx Number level/ppm Rating Rating Rating ing Ratingvacuum traction vacuum traction vacuum traction 1 cycle 3 cycles 5cycles 1 none 9.0 4.0 5.0 5.0 3.5 4.5 3.0 4.0 2.5 3.5 5.0 4.5 4.0 2 120± 50 9.0 3.0 5.0 5.0 3.5 5.0 2.5 4.5 2.5 4.0 5.0 4.0 3.5 3 198 ± 50 9.03.0 5.0 5.0 3.5 5.0 2.5 4.5 2.5 4.0 5.0 4.0 3.5 4 385 ± 50 9.0 4.0 5.05.0 3.5 5.0 2.5 4.5 2.5 4.0 5.0 4.0 3.5

TABLE 2 Wear Bleach Soil Resistance Ratings Red 40 Appear- Color UVLight 1 cycle 1 cycle 3 cycles 3 cycles 5 cycles 5 cycles ExampleFluorine Stain ance Change Weather- dry wet ex- dry wet ex- dry wet ex-Colorfastness to NOx Number level/ppm Rating Rating Rating ing Ratingvacuum traction vacuum traction vacuum traction 1 cycle 3 cycles 5cycles  7 120 ± 50 8.5 3.0 5.0 5.0 3.5 5.0 2.5 4.5 2.5 4.5 5.0 4.0 3.5 8 120 ± 50 9.0 3.0 5.0 5.0 4.0 5.0 2.5 4.5 2.5 4.5 5.0 4.0 3.5 11 120 ±50 9.5 4.0 5.0 4.5 4.0 4.5 3.5 4.5 3.5 4.5 5.0 5.0 5.0 12 120 ± 50 9.54.0 5.0 4.5 4.0 4.5 3.5 4.5 3.5 4.5 5.0 4.5 4.5 13 120 ± 50 9.5 4.0 5.04.5 4.0 4.5 3.5 4.5 3.5 4.5 5.0 4.5 4.5 14 120 ± 50 9.5 4.0 5.0 4.5 4.04.5 3.5 4.5 3.5 4.5 5.0 4.5 4.5 15 120 ± 50 9.0 4.0 5.0 4.5 3.5 4.5 3.04.0 2.5 4.0 4.5 3.5 2.5 16 120 ± 50 5.0 4.0 5.0 4.5 3.5 4.5 3.0 4.0 2.53.5 5.0 4.5 4.5

I claim:
 1. A method of producing a stain-resistant and soil-resistantpolyamide yarn comprising the steps of: (a) melt compounding a reagentincluding a metal salt of sulfoisophthalic acid and a thermoplasticpolyester having a melting point of less than 270° C. to produce asulfonated polyester concentrate; (b) adding the sulfonated polyesterconcentrate formed in step (a) to a fiber-forming polyamide to form afiber-forming polyamide composition, at least a portion of the melt saltof sulfoisophthalic acid associating with free acid dye sites in saidpolyamide; (c) melt extrusion spinning said fiber-forming polyamidecomposition to form yarns, and (d) drawing and texturing said yarns toproduce a multiplicity of bulked continuous filaments therein.
 2. Themethod of claim 1, wherein said sulfonated polyester concentratecontains about 10 to about 65% by weight of said reagent.
 3. The methodof claim 1, wherein said thermoplastic polyester is selected from thegroup consisting of PET, PTT, PBT, PETG, poly(ethyleneterephthalate-co-isophthalate), and mixtures thereof.
 4. The method ofclaim 1, wherein said reagent is a metal salt of 5-sulfoisophthalicacid.
 5. The method of claim 4, wherein said salt is an alkali metalsalt of 5-sulfoisophthalic acid.
 6. The method of claim 5, wherein saidalkali metal salt is the lithium salt of 5-sulfoisophthalic acid.
 7. Themethod of claim 5, wherein said alkali metal salt is the sodium salt of5-sulfoisophthalic acid.
 8. The method of claim 1, wherein saidfiber-forming polyamide is selected from the group consisting of PA6,PA66, copolymers of PA6 and PA66, and mixtures thereof.
 9. The method ofclaim 1, wherein said fiber-forming polyamide has a relative solutionviscosity of between about 2.9 and about 4.0.
 10. The method of claim 1,wherein said fiber-forming polyamide has an amine end group level ofless than about 35 equivalents per 10⁶ g.
 11. The method of claim 1,additionally containing an adjuvant.
 12. The method of claim 11, whereinsaid adjuvant is selected from the group consisting of an anti-oxidant,a stabilizer, a colorant, a processing aid, a nucleating agent, anantimicrobial, a melt viscosity enhancer, a flame retardant, andmixtures thereof.
 13. The method of claim 1, wherein said compositioncontains between about 1000 and about 3000 ppm of sulfur.